Today's refineries use large volumes of hydrogen for hydro-processing applications geared towards clean-fuels production and yield enhancements. Similarly, most biofuels processes require large volumes of hydrogen in order to produce drop-in fuels. In the past, refineries produced hydrogen primarily as a byproduct of catalytic naphtha reforming, a process for producing high-octane gasoline. However, increased processing of sour and heavy crudes, coupled with stricter environmental regulations, have significantly increased refinery hydrogen requirements. Consequently, most refineries today use steam methane reforming (SMR) to provide the supplemental hydrogen. Individual refinery hydrogen demand varies, depending on the crude slate and complexity. Although SMR is a matured technology, it has a significant carbon footprint. An average capacity SMR, 45 million standard cubic feed per day (MMSCFD) of hydrogen, generates around 59 pounds of CO2/thousand standard cubic feed of hydrogen, excluding credits from steam export.
The CO2 emission from the SMR comes from the steam reforming reaction and from the fuel combustion that provides the required heat for the reforming reaction. The fuel consists of natural gas and supplementary off-gas from the pressure swing absorber (PSA) used to separate the hydrogen produced from the other SNIT process effluents. The PSA off-gas mostly consists of CO2 (produced from the steam reforming reaction), CO, slip hydrogen, and un-reacted methane. In this configuration, all of the CO2 from the unit (combustion and steam reforming) exits the process area as part of the flue gas via the furnace stack, where the residual CO2 concentration is relatively dilute. In principle, conventional amine-based scrubber technologies could be employed to capture the CO2 from the SMR. However this process is very expensive.
On the other hand, steam reforming of single or multi-component oxygenated bio-feeds having a molecular formula of CxHyOz (where z/x ranges from 0.1 to 1.0 and y/z ranges from 2.0 to 3.0) could be an alternative source of low carbon hydrogen. However, at relevant reforming conditions, the longevity of conventional Ni-based reforming catalysts is significantly reduced during the reforming of bio-derived oxygenates, primarily due to the rapid formation of carbonaceous deposits.
There exists a need for formulations of relatively inexpensive catalysts that effectively pre-convert bio-derived oxygenates mostly to hydrogen, carbon dioxide, carbon monoxide, and methane with superior coking resistance relative to conventional reforming catalysts.